Process and product for the stabilizing of unsaturated hydrocarbons



Patented June 22, 19537 PROCESS AND PRODUCT FOR THE STA- BILIZING OFUNSAT'URAT'ED HYDROCAR- BONS Charles P. Wilson, Jr., Houston, Tex.

' No Drawing. Application August 15, 1984,

Serial No. 739,934

6 Claims.

This invention relates to a method of preventing deterioration of oils,fats, and rubber, and is applicable to substances liable to oxidation.The process and product will be described more particularly in relationto inhibiting auto-oxidation of motor fuels resulting from pyrolysis ofheavy oils or coal.

Color deterioration and gum formation are known to be the result ofoxidation. Color de- 0 terloration does not. render motor fuel or motoroil unfit for use, but lowers its market value. Gum formation is theresult of oxidation of unsaturated hydrocarbons, and when present inmotor fuel in small quantities renders the fuel unfit for use in aninternal combustion engine. To obtain gum-free and stable products, theusual practice is to remove a substantial quantity of the unsaturatedhydrocarbons through treatment with sulfuric acid. or through thecontrol of the cracking plant in such a manner as not to produce a highconcentration of the unstable unsaturated hydrocarbons. Control of thecracking process in this way sometimes results in a lower percentage 5of cracked fuel, and the sulfuric acid treatment always results ina'loss, which in many cases runs as high as 5% of the motor fuelproduced. This treatment is costly and wasteful, and also results in alowering of the anti-knock value of the motor fuel.

The primary object of the invention is the manufacture and use of anoxidation inhibitor which, when added in minute quantities, preventsdeterioration of hydrocarbons and various oils liable to oxidation. Itis particularly useful in the manufacture and marketing of motor fuelcontaining unsatura..-d hydrocarbons liable to oxidation. since it notonly inhibits gum formation in storage, but actually reduces the gun'yield 40 when the cracked product to which the inhibitor has beenadded is tested for gum bythe copper dish method. In the majority ofcasesonly a minute quantity of the inhibitor, the cost of which isalmost negligible, is required to reduce the result of the copper dishtest to any desired speciflcation, Results of tests made with identicalcracked gasolines with and without the addition of the stabilizingcompound are shown hereunder:

I have found that the following substances are effective in preventinggum formation when added in minute quantities to oils:

Pyrogallol Para-aminophenol Catechol Para-phenylenediamine HydroquinoneMethylaminophenol 25 Ortho-aminophenol Alpha-naphthol Numerous othercompounds, such as cresol, dimethylaniline, etc., have a slightstabilizing effeet, but my experience has been that as a general ruleonly aromatic compounds with two 30 hydroxyl and/or amino groups in theortho or para positions of the benzene ring will completely preventoxidation, although it will be noted that alpha-naphthol, which has onlyone hydroxyl group, is an exception. e presence of other, groups in thebenzene ring in addition to the above mentioned does not destroy theinhibiting action.

All of the above mentioned substances except 40 alpha-naphthol are moresoluble in water than in oil, in which they are nearly insoluble, andthey are not satisfactory for use in practice for the commercialstabilization of motor fuels on account of the fact that it is diilicultto prevent 45 the latter from coming into contact with water. Naphtholcannot be used, since it causes motor fuel to deteriorate in color,although it is satisfactory as regards solubility.

I have found that if an alkyl or aryl group is substituted for ahydrogen atom in these compounds, their solubility in water is decreasedand their solubility in oil is increased wthout an appreciable loss intheir power to inhibit oxidation. The greater the number of alkyl oraryl groups which can be substituted in thebenzene ring, the moresoluble is the resulting compound in the hydrocarbon to be stabilizedand the less soluble in water.

The new and novel features of the present invention are: the productionof oil-soluble oxidation inhibitors from certain types of oil-insolublephenolic or amino compounds, by substitution of one or more alkyl oraryl groups for hydrogen atoms; an improved method of introducing analkyl group into a phenol; and the utilization of turpentine, a liquidsulfur dioxide extract of an oil, or the unsaturated hydrocarbonsderived from the pyrolysis of oil or coal, as the base or stock fromwhich the substituted phenolic or amino compound is produced; oilscontaining mixed unsaturated hydrocarbons are very much cheaper than thepure unsaturated compounds, but are equally satisfactory for thepreparation of the substituted compound.

The introduction of alkyl groups is effected by a modification of themethod of Koenigs (Ber. 23, 3144; 24, 179, 3889; 25, 2649) who preparedalkyl substituted phenols by allowing a mixture of one part of thephenol with the equivalent amount of an unsaturated hydrocarbon to standfor several days in the presence of one part of concentrated sulfuricacid and nine parts of acetic acid. My improvements that are new to theart are as follows:

1. The use of a mixture of unsaturated hydrocarbons, such as turpentine,a liquid sulfur dioxide extract of an oil, or an oil derived from thepyrolysis of oil or coal. Such oils should preferably contain a largepercentage of unsaturated hydrocarbons, as high concentrations of thelatter cause the reaction to take place more readily.

2.' The use of dilute sulfuric acid (about 50%) instead of concentratedacid. This prevents loss of the phenolic compound by eliminating sidereactions such as the formation of acetates.

3. The use of a much smaller quantity of sulfuric and acetic acid, thusreducing the cost of manufacture.

4. Carrying out the reaction at an elevated temperature with agitation.This reduces the time required to a few hours.

5. The use of a considerable excess of unsaturated compounds, in orderto avoid loss of the more costly phenol.

6. Incomplete removal of acetic acid from the solution of alkylsubstituted phenol. A trace of acid present in the solution acts as apreservative, preventing oxidation of the compound itself before it isadded to the oil to be stabilized.

7. The use of a dilute solution of a mineral acid for extracting theacetic acid instead of water or ammonium carbonate. Oxidation of thecompound during the washing is thus prevented.

It will be noted that by alkylation of the various oil-insolubleoxidation inhibitors, such as pyrogallol and aminophenol, in variousways, an almost infinite number of different compounds can be obtainedwhich would be suitable for inhibiting the oxidation of oils. For thepreparation of the various types of compounds, a number of diiferentmethods are available. For example,

amyl pyrogallol may be prepared by the action of amyl alcohol onpyrogallol in the presence of anhydrous zinc chloride; and aminophenolcan be alkylated by heating under pressure with alcohols; or thereaction between pyrogailol and unsaturated hydrocarbons will take placeto some extent without a catalyst, or with aluminum chloride. I have,however, found that the cheapest and easiest compounds to manufactureare those prepared from py ogallol by the method described above.Catechol also gives good results by this method, but is more expensive.Examples of the preferred method of preparation using cracked distillateand turpentine are given below:

Five parts by Weight of powdered pyrogallol, ten parts of glacial aceticacid, one part of 50% sulfuric acid, and ten parts of cracked distillateare placed in an acid-resisting container fitted with a stirrer and areflux condenser, and supplied with facilities for heating. The mixtureis agitated violently, and heated to boiling. The agitation and heatingare continued for two hours, 75 parts of cracked distillate beinggradually added during this period. After two hours, when substantiallyall of the pyrogallol should have entered into combination with theunsaturated hydrocarbons present, the agitation is stopped and theproduct allowed to cool in an oxygen-free atmosphere. The reaction whichoccurs is probably as follows:

R.CH:CHg plus C HMOH); gives RCH .CH .C H (OHJ.

oleflne pyrogallol stabilizer The resulting mixture consists of asolution of the oxidation inhibitor and acetic acid in the oil whichsupplied the unsaturated hydrocarhens, and a layer of sludge on thebottom of the containing vessel. Twenty parts of 0.1% sulfuric acid areintroduced, and the mixture is agitated for fifteen minutes for thepurpose of removing excess acetic acid. The washing also causes anysubstituted compound contained in the sludge to return to the oilsolution. The lower layer is drained off, and the extraction repeatedtwice. The solution of oxidation inhibitor thus prepared is then runinto a storage vessel. preferably of copper or wood.

When turpentine is used, forty parts of pyrogallol are dissolved byheating and agitation in sixty parts of glacial acetic acid. One part of50% sulfuric acid is added, and a hundred parts fresh turpentineintroduced while he mixture is being agitated. Heat is evolved, and caremust be taken that the temperature does not rise above 100 C. When allthe turpentine has been added, the mixture is maintained at about C.until the reaction is substantially complete. After cooling, it may bediluted by a suitable oil. It is then washed as in the previous example.The amount of the substituted compound formed is substantially twice theweight of pyrogallol used. I have found that acetic acid acts as apreservative of the compound, but most of it must be removed as it wouldcause the motor fuel to which the above described inhibitor has beenadded to become corrosive. The acetic acid may be removed by extractionwith any suitable solvent, such as water or a mineral acid, or by othersuitable methods such as distillation, instead of by dilute sulfuricacid as described in the above examples.

Referring more particularly to the use of a sulfur dioxide extract of anoil, mentioned here- -tofore, I have found it advantageous to use ancracked distillate obtained by cracking a gas oil from a mixed basecrude. The cracking may be done in the liquid or vapor phase, but theinvention may find best application in treating a distillate that is notextensively cracked, such as that from a liquid or semi-liquid phasecracking i operation wherein the unsaturated content may vary from10-30%, since the highly cracked vapor phase distillates containing40-60% unsaturation may be used as such without further concentration ofthe unsaturatedconstituents. While I have mentioned specifically theextraction with liquid sulfur dioxide, I may use other solvents,

- such as furfural, nitrobenzene, phenol or mixtures thereof withmodifying solvents, which function in a substantially equivalent mannerto sulfur dioxide, 1. e. which effect a separation of constituentsuseful in my invention from the distillate extracted.

In the extraction of the cracked distillate the procedure may be thesame as ordinarily fol- 'lowed in the prior art for treating suchdistillates. The extraction is usually carried out at a low temperature,say around zero, in the case of liquid sulfur dioxide or at a somewhathigher temperature with a correspondingly higher pressure in order tomaintain the solvent in the liquid phase. The ratio of solvent to oilmay be ad- 'justed to effect the required separation and this willreadily be done by the skilled operator. The extraction should beconducted so that a large proportion of the unsaturated constituents ofthe oil is extracted by the solvent. Aromatic hydrocarbons and asubstantial amount of sulfur compounds, if present, will also beextracted but these are usually not objectionable. In case the amount ofsulfur compounds is large, it may be reduced by treating with sulfuricacid or other suitable desulfurizing operation.

The extract is readily recovered from the solvent by vaporization of thesolvent; for example, inthe case of sulfur dioxide the solvent readilyvolatilizes on release of the pressure. The quantity of extract willvary with the oil treated but usually runs from about 15-30% of thedistillate. It is highly unsaturated and normally of slightly highergravity and boiling point than the original mercial cracking operation,such as the Holmes- Manley, was treated with liquid sulfur dioxide andthe oil separated into an upper layer, comri ing about 80% of thedistillate treated, and a lower layer, containing about 20% of theoriginal oil dissolved in liquid sulfur dioxide. The lower layer wasseparated fromthe upper layer and the sulfur dioxide removed bydistillation.

The remaining oil was washed with caustic soda to remove the remainderof the sulfur dioxid and some of the other sulfur compounds. Five partsof pyrogallol, ten parts of glacial acetic acid, one part of 50%sulfuric acid were mixed with ten parts of the extract and the mixturerefluxed for about two hours during which time 40 parts more of theextract were gradually. added. The mixture was then cooled and theexcess acids washed out with 0.1% sulfuric acid. The product was thenready for use as a gum inhibitor.

It has been found that the substituted compound when prepared asdescribed above may be stored for a long period of time, at least aslong as two years as shown by practical tests, without losing activityas a stabilizer.

I have found that a compound as thus pre pared is acidic and that it canbe removed or destroyed by shaking with alkalies, such as sodiumcarbonate or caustic soda. It i"s,"therefore, necessary to prevent themotor fuel from coming into contact with alkaline substances after theaddition of the inhibitor. The compound is also destroyed by organicperoxides, and to prevent this it is advantageous that the motor fuel befresh and free from peroxides when the compound is added.

The gum content of samples 3 and 4 shown hereunder has been determinedby the U. S. Bureau of Mines Steam Oven Method, in which a 20 cc. sampleof motor fuel is evaporated in a steam oven from which oxygen isexcluded. The gummy residue obtained in this manner is considered torepresent the actual or inherent gum present in the fuel.

The gum content of samples 1 and 2 hereinbefore described under copperdish tests was determined by evaporating 100 cc. of cracked gasoline ona steam bath. In this test the gasoline is exposed to atmospheric oxygenduring the evaporation and although a sample of cracked gasoline gives aconsiderable residue by this method, the same sample might be found tobe entirely free from inherent gum as determined by the steam ovenmethod.

Results of storage tests made on identical cracked gasolines, with andwithout addition of inhibitor, are given below. The samples consist ofcracked gasoline stored in dark in glass bottles vented to atmosphere:

Sample No. 3

Steam oven gum Color, Saybolt (gins. per 20 cc.) chromometer Time ofstorage (weeks) With 0 001 w 11 Without Without percent ercent Winhibitor nhlbim iz ihibitor Nil lus 25 1 Nil p 25 p us Nil 25 25 Nil 2525 Nil 25 25 Ni! 25 25 1 Nil 25 25 23 Nil plus 17 25 29 Nil 25 N11 25 41Nil plus 24 Nil 22 59 Nil 3 71 23 Sample 1V0. 4

Steam over gum (gins. Color, Saybolt chroper 20 cc.) mometer Tinte oistorage wee 5 With 0.0005 With 0.0005 Without Without percent inpercentininhibitor humor inhibitor hibitor Nil Plus 25 Plus 25 Nil 25 25 Trace25 25 Ni] 25 25 Nil 25 25 Nil Plus 22 25 Nil Plus 21 25 Plus 24 24 23 21From the above description it will be evident that while I havedescribed and claimed the preferred embodiment of the invention, it isto be understood that I reserve the right to make all changes properlyfalling within the spirit of the invention and without the ambit of theprior art.

This application is a continuation in part of my application Serial No.730,728, filed June 15, 1984, which in turn is a continuation of SerialNo. 503,095, filed December 17, 1930.

I claim:

1. The method of inhibiting gum formation in low boiling liquid crackedhydrocarbon distillates, which comprises incorporating in the distillatea small amount of polyhydric phenol derivatives, said derivativescontaining, as substituted groups, unsaturated constituents extractedfrom cracked naphtha by sulfur dioxide.

2. A low boiling liquid cracked hydrocarbon distillate, normally tendingto deteriorate and form gum on storage, and containing a small amount ofpolyhydric phenol derivatives, whereby such deterioration and gumformation are substantially retarded, said derivatives containing, assubstituted groups, unsaturated constituents extracted from a crackednaphtha by sulfur dioxide.

3. The method of inhibiting gum formation in cracked hydrocarbondistillates of the class of gasoline and kerosene, which comprisesadding to the distillate a small proportion of a condensation product ofa sulfur dioxide extract of a cracked naphtha and a polyhydric phenol ofthe class having hydroxyl groups in the ortho and para position, saidcondensation product consisting essentially of a mixture of substitutedpolyhydric phenols containing components of said extract as substitutedgroups.

4. The method of inhibiting gum formation in cracked gasoline, whichcomprises adding to the gasoline a small amount of a condensationproduct of pyrogallol and a sulfur dioxide extract of crackedhydrocarbon distillate, said condensation product consisting essentiallyof a mixture of pyrogallol derivatives containing hydrocarbon componentsof said extract as substituted groups.

5. A cracked gasoline, normally tending to deteriorate and form gum onstorage, and containing, in sufficient amount to substantially retardsuch deterioration and gum formation, a condensation product of a sulfurdioxide extract of a cracked hydrocarbon distillate and a polyhydricphenol of the class having hydroxyl groups in the ortho and parapositions, said condensation product consisting essentially of a mixtureof substituted polyhydric phenols carrying as substituted grouphydrocarbon components of said extract.

6. A cracked gasoline, normally tending to deteriorate and form gum onstorage, and containing a small proportion of a condensation product ofpyrogallol and a solvent extract of a cracked naphtha to retard saiddeterioration and gum formation, said condensation product consistingessentially of a mixture of pyrogallol derivatives carrying componentsof said extract as substituted groups.

CHARLES P. WILSON, Jn.

